Three key points of an oscilloscope: bandwidth, sampling rate, and storage depth
Bandwidth, sampling rate and storage depth are the three key indicators of digital oscilloscopes. Compared with engineers' familiarity with and emphasis on oscilloscope bandwidth, sampling rate and storage depth are often overlooked in the selection, evaluation and testing of oscilloscopes. The purpose of this article is to help engineers better understand the important characteristics of the two indicators of sampling rate and storage depth and their impact on actual testing by briefly introducing the relevant theories of sampling rate and storage depth combined with common applications. It also helps We understand the trade-offs when choosing an oscilloscope and establish the correct concept of using an oscilloscope.
Before we begin to understand the related concepts of sampling and storage, let's review how a digital storage oscilloscope works.
The input voltage signal is sent to the front-end amplifier through the coupling circuit, and the front-end amplifier amplifies the signal to improve the sensitivity and dynamic range of the oscilloscope. The signal output by the amplifier is sampled by the sample/hold circuit and digitized by the A/D converter. After A/D conversion, the signal becomes a digital form and is stored in the memory. The microprocessor processes the digitized signal waveform in the memory. Corresponding processing is performed and displayed on the display. This is how a digital storage oscilloscope works.
Sampling, sampling rate
We know that computers can only process discrete digital signals. The primary problem faced after the analog voltage signal enters the oscilloscope is the digitization (analog/digital conversion) of the continuous signal. Generally, the process from continuous signals to discrete signals is called sampling. Continuous signals must be sampled and quantized before they can be processed by computers. Therefore, sampling is the basis for waveform calculation and analysis by digital oscilloscopes. By measuring the voltage amplitude of a waveform at equal time intervals and converting the voltage into digital information represented by an eight-bit binary code, this is the sampling of a digital storage oscilloscope. The smaller the time interval between sampling voltages, the closer the reconstructed waveform is to the original signal. Sampling rate is the sampling time interval. For example, if the sampling rate of the oscilloscope is 10G times per second (10GSa/s), it means that a sample is taken every 100ps.
